18 The Open Waste Management Journal, 2010, 3, 18-25 1876-4002/10 2010 Bentham Open Open Access Used Foundry Sand in Cement Mortars and Concrete Production Saveria Monosi, Daniela Sani * and Francesca Tittarelli Università Politecnica delle Marche, Dipartimento di Fisica, Ingegneria dei Materiali e del Territorio (FIMET), Italy Abstract: Used foundry sands represent the highest amount of solid wastes generated by foundries. Classified by European Union regulations as non hazardous waste, they represent a relevant source to be reused in several industrial sectors, in building construction primarily. In present paper, the properties of mortars and concretes containing different dosages of used foundry sand (UFS) as partial replacement of sand were investigated in both fresh and hardened conditions. In particular, higher percentages of addition, but lower if referred to the whole aggregate (fine and coarse), were considered in concretes than in mortars. Both mortars and concretes were evaluated with respect to consistency of the fresh mixture and compressive strength of the hardened material. Elastic modulus determination of the hardened material was carried out on concretes. A low (10%) amount of used foundry sand does not change the mortar‘s performances. In the presence of higher additions a workability decreasing can be outlined, and then a higher dosage of superplasticizer is required in order to keep it constant. Mechanical performances lower of about 20-30% than those of the conglomerate without used foundry sand are observed. The higher penalization it seems to concern to the conglomerates of better quality (i.e. lower water-cement ratio). Keywords: Used foundry sand, spent foundry sand, concrete compressive strength, mortar compressive strength, concrete aggregate replacing, mortar aggregate replacing. INTRODUCTION Used Foundry sand (UFS) is a discarded material coming from ferrous and nonferrous metal-casting industry. It’s a mixture of high quality size-specific silica sand, few amount of impurity of ferrous and nonferrous by-products from the metal casting process itself and a variety of binders. The silica sand is used as moulding material, for ferrous (iron and steel) and nonferrous (copper, aluminium, brass) metal castings, mainly because of its thermal conductivity. The raw sand is normally of a higher quality than the typical bank run or natural sands used in fill construction sites. In the casting process, moulding sands are recycled and reused multiple times, small residues of ferrous and non-ferrous by- products often come from the recycling process. Before to be reused, silica sand needs to be cleaned by means of screening systems and magnetic separators to segregate reusable sand from other wastes and to separate particles of varying sizes [1, 2]. As moulding material, the sand is compacted and shaped according to the mould pattern that is going to be produced, as well as to create cavities that are not practical to produce by normal moulding operations, the cores. Because of that, UFSs contain a variety of binders (a binder is required to give binding action to the incoherent sandy mixtures) depending on the specific application for which they were used. *Address correspondence to this author at the Università Politecnica delle Marche, Dipartimento di Fisica, Ingegneria dei Materiali e del Territorio (FIMET), Italy; Tel: +39 071 2204726; Fax: +39 071 2204627; E-mail: [email protected] Although UFS is partially a recycled material itself, as successfully recycled and reused through many production cycles, after many times it loses its characteristics especially the cleanliness and the uniformity ones. Becoming unsuitable in the manufacturing process, it’s discarded as waste. Typically, the automotive industry and its parts suppliers are the major generators of foundry sand (about 95% of the estimated UFS). They employ about 1 ton of foundry sand for each ton of iron or steel casting produced, with a non negligible impact especially from a sustainable development point of view. According to the American Foundry Society (AFS), a metal casting industry group, the metal-casting process generates 9.4 million tons of foundry sand annually (2007 data) [3]. At present, although a great attention to environmental issues, the general trend is still to dispose UFSs in landfills, sometimes utilised as landfill daily cover. The American Foundry Society estimates that 6.8 million tons of foundry sand (2007 data) [3] was disposed in landfills, approximately the 2/3 of the total production. Several evident drawbacks could be listed due to this trend: early closure of the material life cycle with consequently more consumption of virgin raw materials; saturation of existing landfills and soil pollution in unmanaged landfill cases; release of leachable contaminants, absorbed by the sand during the moulding process and casting operations, like heavy metals (cadmium, lead, copper, nickel, and zinc) and phenols;
Used Foundry Sand in Cement Mortars and Concrete Production
Apr 26, 2023
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